1. Field of the Invention
The present invention relates in general to compact disk players, and more particularly to a compact disk player of the data storage type in which data on a compact disk is stored in a RAM section and the stored data is outputted from the RAM section when the reproduction of the data on the compact disk is discontinued, so that a sound can be prevented from being discontinued due to a vibration such as jolt of vehicles.
2. Description of the Prior Art
Conventional compact disk players comprise pickup means for rotating a compact disk and scanning a laser beam on the compact disk being rotated, servo control means for controlling the pickup means, radio frequency (RF) processing means for converting an analog signal corresponding to an amount of the laser beam reflected on the compact disk into a digital signal, digital signal processing (DSP) means for processing the digital signal from the RF processing means under a control of a microcomputer and controlling the servo control means in accordance with the processed signal, digital/analog (D/A) conversion means for converting the processed signal from the DSP means into an analog signal, and amplification means for amplifying the analog signal from the D/A conversion means and outputting the amplified signal to a speaker. One example of this form of compact disk players is shown in a block form in FIG. 1.
As shown in FIG. 1, the conventional compact disk player comprises a pickup 10 being operated under a control of a servo control device 20. The pickup 10 includes a CD motor 11 for rotating a compact disk 12 under the control of the servo control device 20. In the pickup 10, a laser beam 13 is vertically scanned on the surface of the compact disk 12 being rotated by the CD motor 11. A RF processor 30 is adapted to convert an analog signal corresponding to an amount of the laser beam 13 reflected on the compact disk 12 into a digital signal. A DSP unit 40 is adapted to process the digital signal from the RF processor 30 under a control of a microcomputer 50 and control the servo control device 20 in accordance with the processed signal. The processed signal from the DSP unit 40 is also applied to a D/A converter 60, which converts the applied signal into an analog signal and outputs the analog-converted signal to an amplifier 70. Also, the output signal from the DSP unit 40 is applied to the microcomputer 50. In response to the output signal from the DSP unit 40, the microcomputer 50 controls a display unit (not shown). The amplifier 70 acts to amplify the analog signal from the D/A converter 60 and output the amplified signal to a speaker SP.
In the above-mentioned conventional compact disk player, data is recorded in the form of high and low levels on the compact disk 12, resulting in reduction in a noise component. Also, since the data recorded on the compact disk 12 is reproduced by reading the amount of the laser beam 13 reflected on the compact disk 12, the compact disk 12 is prevented from being worn away. As a result, the life of the compact disk 12 is semi-permanent. However, in the case where the conventional compact disk player is used in vehicles, the focus of the laser beam 13 may be not constant due to jolt of the vehicles or an unsteady state of load surface. For this reason, the pickup 10 cannot smoothly read the data from the compact disk 12, resulting in a discontinuity of a sound. This degrades the reliability of manufactured goods.
Also, in video tape recorders (VTRs) or video disk players, a video format signal is read from a video memory, being delayed by one frame. For the purpose of avoiding an error in reproducing a video picture, a horizontal synchronizing signal HS' is generated being shifted by one period of an original horizontal synchronizing signal HS of a composite vidoe signal. X and Y address counters generate X and Y addresses in response to the horizontal synchronizing signals HS and HS'. The video format signal is stored in a location of the video memory corresponding to the X and Y addresses from the X and Y address counters. As a result, the video picture can be reproduced with no damage. One example of these techniques is shown in Japanese Patent Laid-open Publication No. Heisei 1-164188. However, the above Japanese Patent is desirable to read the video format signal from the video memory with no error, but has the disadvantage that it cannot propose how to cope with the faulty operation of the pickup (head) resulting from the vibration such as the jolt of vehicles.